Conventionally, because of the increase of environmental awareness and the rise in energy prices, the demand for efficient use of electric power is increasing in various fields. In offices, in order to aim at energy conservation of a whole department, individual use of electric power is grasped in small unit. In recent years, an energy management system to grasp power consumption of individuals by distributing power outlets, which have power measuring function, called smart outlets is popular.
Such an energy management system increases cost in an office where layout is often changed, in a conference room having outlets whose users often change, in an office where individual desks are not fixed, called non-territorial office, and the like. Therefore, a mechanism for automatically linking appliances and outlets are proposed.
For example, there is a known method for equipping plugs with RFIDs (Radio Frequency Identification) having IDs of appliances, and for reading the RFIDs by RFID readers provided in outlets so as to associate appliances and outlets. In addition, there is a known method for outputting a command to generate a specific power consumption pattern from a server to an appliance, and for detecting the same power pattern on the outlet side, thereby associating appliances and outlets. Further, there is a known technique of sending an appliance ID when the condition of the appliance changes, and of associating the appliance with an outlet having power change at that time. Related-art examples are described in Japanese Laid-open Patent Publication No. 2006-228225, Japanese Laid-open Patent Publication No. 2011-197931, and Japanese Laid-open Patent Publication No. 2004-134920.
However, the technique that uses RFID increases cost since special outlets with RFIDs are used. In addition, the technique that outputs a command from server decreases usability since resource is consumed regardless of the intention of users. Further, the technique that sends an appliance ID increases a rate of erroneous decision since the number of outlets whose power change at the same time is large in an environment where multiple appliances operate at the same time, such as in an office.
On the other hand, there is also a conceivable technique that links time-series data of power consumption measured at outlets and resource consumption data of electric appliances such as PCs plugged into the outlets by calculating correlation therebetween. However, this technique is difficult to secure scalability, and thus it is difficult to control the frequency of performing the link process, which is disadvantageous.
Specifically, since a link of actual appliances dynamically changes by various factors, it is desirable to update link data in real time to follow the change. Therefore, data is periodically acquired in order to address a case where event load information is difficult to be registered from an appliance side upon movement of the appliance in a case where a network environment is difficult to be provided immediately, for example. However, in order to frequently update the correlation, information is acquired and correlation is calculated frequently. These processes deteriorate performance of a server that calculates the correlation. As described above, it is difficult to secure scalability, and thus the frequency of performing the link process is difficult to be appropriately controlled.